Spraying device, more particularly for abrasive liquid compositions

ABSTRACT

A membrane gun for spraying abrasive liquids has a membrane supported around its full periphery in a chamber in the body of the membrane gun, a first surface of the membrane forming a wall of this chamber. A tubular member is supported in the chamber with a free end facing the membrane. A second surface of the membrane is acted on variably by a composite plunger of a singleacting pneumatic cylinder. The liquid is admitted to the chamber and must pass over the free end of the tubular member to enter the interior of their member and be expelled from the gun through a nozzle. Regulation of the plunger regulates the distance of the membrane from the tubular member and thus the flow through the gun. The pneumatic cylinder is arranged coaxially with the body of the gun to occupy the minimum lateral space.

United States Patent Vicentini et al.

[54] SPRAYING DEVICE, MORE PARTICULARLY FOR ABRASIVE LIQUID COMPOSITIONS[72] lnventorsz'Giorgio Vicentini; Giulio Console, both of Turin, Italy[73] Assignee: Boeri di A.G. Boeri & C., Turin,

Italy [22] Filed: June 18, 1971 [21] Appl. No.: 154,375

[30] Foreign Application Priority Data June 25, 1970 ltaly "69198 A/70[52] us. Cl. ..239/92,239/296,'239/412 s11 rm. Cl. ..-B05b 1/30 [58]Field of Search ..239/88, 92, 410, 41 1, 412, Y 239/296; 251/6l.1, 62,331

[56] I References Cited UNITED STATES PATENTS 3,622,078 11/1971 Gronert..239/412 X [451 Dec. 12,1972

3,424,385 1/1969 Gutermann eta] ..239/4l2 3,194,502 7/1965 West..239/411 Primary Examiner-M. Henson Wood, Jr. AssistantExaminer-Michael Y. Mar Attorney-Richard C. Sughrue et a].

[5 7] ABSTRACT A membrane gun for spraying abrasive liquids has amembrane supported around its full periphery in a chamber in the body ofthe membrane gun, a first surface of the membrane forming a wall of thischamber. A tubular member is supported in the chamber with a free endfacing the membrane. A second surface of the membrane is acted onvariably by a composite plunger of a single-acting pneumatic cylinder.The liquid is admitted to the chamber and must pass over the free end ofthe tubular member to enter the interior of their member and be expelledfrom the gun through a nozzle. Regulation of the plunger regulates thedistance of the membrane from the tubular member and thus the flowthrough the gun. The pneumatic cylinder is arranged coaxially with thebody of the gun to occupy the minimum lateral space.

4 Claims, 4 Draiving Figures PAIENTED E 12 I972 3.705.687

- SHEET 3 0F 3 Fig. 5

This invention relates to a spraying device for abrasive liquidcompositions.

The use of abrasive liquid compositions for polishing has become common.These compositions differ greatly from one another in theircharacteristics, and their viscosity, which is a very important factoras regards spraying, varies from 6,000 to 180,000 cps.

Spray guns of the type used for spraying paints and the like were atfirst used for spraying abrasive liquid compositions. In these guns aneedle valve capable of being actuated from outside is provided in aduct through which the material to be sprayed is supplied, and thesupply of material is regulated by means of this valve. When thismaterial consists of an abrasive liquid composition the excessive wearto which the needle valve is subjected makes the gun unserviceable in ashort time, and it is therefore clear that the gun is unsuitable forthis purpose.

, The guns described above were thus of little practical utility, andwere soon replaced by spraying devices more suitable for abrasive liquidcompositions and known as membrane guns. The membrane gun generallycomprises an elongated substantially cylindrical body having inside it aduct which communicates at one end with the supply system and at theother end with an ejector nozzle. The body is also provided with agenerally radial connector incorporating a duct through which compressedair is supplied. Inside the duct through which the abrasive compositionis supplied there is usually a transverse diaphragm which cooperates qtits edge with the surface of a membrane. The membrane when in contactwith this diaphragm closes the supply duct, whereas the membrane whenseparated from the diaphragm permits the abrasive composition to passbetween the membrane and the free edge of the diaphragm.

A device for controlling the open position of the membrane is arrangedradially on the cylindrical body. This device is generally of the all ornothing type or, more rarely, consists of a pneumatic cylinder andregulating device, of very cumbersome structure and difficult tomanipulate,-which is adapted to permit the membrane to assume more thanone open position. The regulating device acts on the membrane so as tolimit the displacement of the membrane, the arrangement being such thatthe membrane, when not displaced completely blocks the duct throughwhich the abrasive material is supplied.

For very low operating pressures, the side of the membrane remote fromthe diaphragm is provided with a projection adapted to connect themembrane with the control device. In this case the abrasive liquidcomposition is supplied at a pressure which does not permit resilientdeformation of the membrane itself.

During the polishing operations the membrane guns are generally mountedon a casing known as a hood which covers one or more polishing drums.These drums are rotatably mounted on a shaft and are disposedtangentially to the surface to be polished.

, The membrane guns described above have numerous disadvantages. Aboveall, the abrasive composition feed is generally axial, whereas theatomizing air feed and the device for controlling the position of themembrane are arranged radially and spaced apart from one another. As aconsequence, the group of supply ducts connected to the gun is verybulky and does not permit easy and convenient arrangement of this gun onthe hood.

Another disadvantage of the known membrane guns is that, because of thebulk of thedevice for controlling the position of the membrane, thediaphragm is located at a relatively great distance from the ejectornozzle. Consequently, when the membrane blocks the supply duct at theend of the spraying operation there is a considerable quantity ofabrasive composition downstream of the diaphragm, and if the viscosityof the abrasive composition is below a certain value this abrasivecomposition drips out.

Since the diaphragm is arranged transversely in the supply duct, it isalso subjected to heavy wear. In membrane guns the diaphragm isgenerally formed integrally with the cylindrical body, and thereforerapid wear of the diaphragm leads to rapid wear of the gun itself, sothat the costs are high.

Known membrane guns'are generally employed in automatic polishing plantsin which a plurality of guns are used and are fed simultaneously by onepressure system and in which the consumption of the abrasive compositionis controlled by two timing devices which set the beginning and'the endof the spraying process. Since all the guns are connected to the samesupply system and since the pressure drops in the connections leading toeach individual gun differ from one gun to another, each gun consumes alarger or smaller quantity of abrasive composition according to whetherthe pressure at which it is fed is larger or smaller. The consequencesof this fact map be very serious inthat they may cause non-uniformpolishing of a workpiece.

In order to avoid this disadvantage in the known membrane guns it wouldbe necessary to regulate the rates of consumption of the abrasivecomposition in accordance with the pressure drops in the supply systemon each of the guns used so as to obtain uniform consumption of theabrasive material and therefore uniform polishing. In order to obtainthis it would be necessary to adopt the expensive solution of providingeach gun with two timing devices adapted to regulate the beginning andthe end of the period of consumption of the abrasive composition.

In order to eliminate this disadvantage, in one known membrane gun theposition of the membrane is controlled by single-acting pneumaticcylinder, and the projecting length of the rod of this cylinder isregulable from outside. In this way, by varying the aperture throughwhich the abrasive composition passes it is possible to regulate thequantity of material sprayed, thus compensating for the non-uniformitiesof feed pressure which are found in the various guns mounted on the sameprotective cap. But because of the position of the pneumatic controlcylinder; this regulation of the projecting length of the rod is verydifficult and not very accurate. It must also be noted that when apneumatic control cylinder of the type described above is used, thetimes which the membrane takes to return to the closed position are verylong and do not permit compositions of very high viscosity to be sprayedunder the best conditions.

than!" [nun The invention provides a spraying device for an abrasiveliquid composition, comprising an elongated body having a longitudinalaxis, a nozzle for ejecting abrasive compositions and atomizing air, thenozzle being connected longitudinally to one end of the body, a passageleading from the exterior into the body and communicating with thenozzle, the abrasive composition being adapted to be admitted throughsuch passage and expelled through the nozzle, a membrane located in suchpassage, and regulating means for varying the position of the membranein order to vary the flow of abrasive composition through the passage;with the improvement that the regulating means includes a longitudinallyarranged single-acting pneumatic cylinder having a plunger adapted toco-operate with the membrane, and a pin member arranged longitudinallyand being adjustable from outside the body to limit the permissiblemovement of the plunger.

Inthe drawings:

FIG. 1 is a diagrammatic cross section through a protective hoodprovided with a spraying device of the invention,

FIG. 2 is a front elevation view on an enlarged scale of the sprayingdevice of FIG. 1, partly broken away to show interior construction;

FIG. 3 is a view on line III III of FIG. 2, and

FIG. 4 is a side view in elevation of part of the spraying device ofFIGS. 1 to 3.

FIG. 1 shows a workpiece 1 to be polished. A plurality of polishingdrums 2 rotatably supported by a shaft 3 are disposed tangentially tothe surface of the workpiece. The polishing drums are protected by aprotective hood 4 which consists of a cylindrically curved sheet 5connected to a suction device (not shown in the drawing) through aconnecting duct 6. The protective hood 4 has a plurality of radial holes7 each provided externally with an inlet funnel 8 rigid with the sheet5.

The end part of a spraying device 9 is arranged in each hole 7 andinside the funnel 8. This device comprises an elongated cylindrical body11 located outside the hood 4 and an ejector nozzle 10 extending axiallyfrom the body 11 and projecting into the funnel 8.

The hood 4 is provided externally with a bracket 12 adjacent each hole7, the bracket connecting one end of a support bar 13 pivotally to thehood. The other end of the bar 13 is mounted in a hole 14 in a bracket15 extending radially from the cylindrical body 11 and rigid with thisbody. Inside the bracket 15 there is an internally screw-threaded hole16 (FIG.2) accommodating a screw 17 adjustable from outside to securethe cylindrical body 1 l in a predetermined position with respect to thehood 4. As is best seen in FIG. 3, the cylindrical body 11 comprises aplurality of parts, the first of which is a body 18 located at the endremote from the nozzle 10. The body 18 is substantially cylindrical andhas a flat end surface 19, a cylindrical cavity 20 being formedcoaxially in the body 18 and ending at the surface 19. On its endopposite the surface 19, the body 18 has a flat annular surface 21 fromwhich a cylindrical projection 22 extends axially. Inside the projection22 is a coaxial bore 23, that communicates with the cavity 20.

A cylindrical rod 24 is slidably mounted inside the hole 23 and extendsinto the cavity 20 where it is integrally connected to an end wall 25 ofa cup-shaped body 26. The free end of this body is provided with aflange 27 bounded externally by a cylindrical surface disposed insealing contact with the cylindrical surface of the cavity 20. Thelength of the rod 24 is such that when the end wall of the body 26touches the end surface'of the cavity 20, a short section at the freeend of the rod 24 extends outside the projection 22.

The open end of the cavity 20 is closed by a disc 28 which is preventedfrom leaving the cavity 20 by a circlip 29 mounted inside this cavity20. The disc 28 is provided with a central threaded hole 30 into which athreaded pin 31 is screwed. The end of this pin outside the cavity 20 isprovided with a knurled'head 32, and the end of the pin inside thecavity 20 is adapted in certain conditions to engage the end wall 25 ofthe body 26. A knurled locking ring 33 screwed on to the pin 31 islocated between the head 32 and the disc 28.

The disc 28 is provided internally with an annular groove 34 which iscoaxial with the pin 31 and accommodates the end of a helical spring 35.The other end of the spring 35 is introduced into the body 26 and bearsagainst the end wall 25. The end portion of the cavity 20, together withthe flange 27 and the external cylindrical surface of the body 26,define an annular chamber 36 which is sealed by means of a seal 37. Thechamber 36 communicates with the exterior through a radial duct (notshown in the drawing) formed inside the body 18 and communicating with aconnector 38 (FIGS. 1, 2, 4, 5) adapted to permit a compressed airsupply tube 39 to be connected to the body 18. The compressed airsupplied through the tube 39 will be referred to as control air.

The cylindrical body 11 also includes an annular body 40 (FIG. 3)fitting around the cylindrical projection 22 and having an externaldiameter equal to the external diameter of the body 18, and acylindrical body 41 of which the external diameter is equal to that ofthe body 18. The cylindrical body 41 is bounded at its ends by two flatsurfaces 42 and 43 and is arranged in contact with the annular body 40.

For interconnecting the bodies 18, 40 and 41, holes 44 and 45 are formedin the bodies 40 and 41 and extend through these bodies coaxially withblind screwthreaded holes 46 formed in the surface 21 of the body 18, toaccommodate screw-threaded bolts 47.

A cylindrical cavity 48 formed in the surface of the body 41 has adiameter equal to the external diameter of the projection 22 and ispartly occupied by the end portion of this projection 22. The cavity 48has a flat end surface 49. A membrane 50 of disc shape is arrangedagainst this surface and is adapted to come into contact centrally withthe free end of the rod 24.

The full periphery of the membrane 50 is kept in contact with thesurface 49 by means of a raised rim 52 of a disc 51 arranged inside thecavity 48. The disc 51 bears against the end surface of the projection22; a central tubular projection 53 integral with the disc fits roundthe rod 24 and is located inside an enlarged end part 54 of the bore 23.By means of its projection 53 the disc 51 closes the cavity 54 and formsthe outer boundary of an annular chamber 55 which communicates with theannular chamber 36 through the gap between the rod 24 and thecylindrical surface of the bore 23. The chamber 55 is sealed at its endnearest the membrane 50 by means of a seal 56.

' A substantially cylindrical projection 57 coaxial with the cylindricalbody 11 extends from the surface 43 of the cylindrical body 41. Acoaxial cavity formed inside theprojection 57 is provided with twoannular grooves 58 and 59 separated from one another by an internallyscrew-threaded annular projection 60. At its inner end the cavity in theprojection 57 terminates in a frustoconical hole 61 communicating with acylindrical hole 62 in the body 41, the other end of this hole 41communicating with a cylindrical cavity 63 closed at one end by themembrane 50. A tubular body 64 is fixed in the hole 62, and projectsinto the cavity 63. It is adapted to contact with the membrane 50 whenthe pressure on both sides of the membrane is equal. 7

A seal 65 is arranged at the end of the cavity defined by the groove 58'inside the projection 57, and cooperates with a frusto-conical section66 of an internal body 67 of the nozzle 10. The body 67 extends into theinterior of the projection 57 and ends in a frusto-conical section 68that co-operates with the surface of the hole 61. The body 67 also has ascrew-threaded section 69'that co-operates with the screw-threadedprojection 60'so as to secure the body 67 against axial-movement withrespect to the cylindrical body 41. The outer surface of'the body 67inside the projection 57 bounds two annular chambers 70 and 71 definedby the grooves 58 and 59. r

In addition to the body 67, the nozzle includes a cap 72 secured to theend of the projection 57 of the cylindrical body 41 by means of a ring73 screwed on to a screw-threaded end of this projection 57. The cap 72has two internal frusto-conical surfaces adapted to cooperate with twoannular frusto-conical projections 74 and 75 of the internal body 67which are separated from one another by a cylindrical section 76.

At its free end the internal body 67 terminates in a conical section 77.This section projects outside through a hole 78 formed centrally in theend of the cap 72. The projections 74 and 75, the section 76 of the body67 and the internal surface of the cap 72 bound an annular chamber 79which communicates with the chamber 70 through an axial duct 80 formedinside the body 67. An axial duct 81 formed inside the cylindrical body41 provides communication between the chambers 70 and 71 and betweenthese chambers and a duct 82 perpendicular to the axis of thecylindrical body 41. The duct 82 leads to the outside and is connectedthrough a connector 83 (FIG. 2) to an external tube 84 through whichatomizing air is supplied.

Two axial projections 85 extending from the end wall of the cap 72 arelocated outwardly of the hole 78 in diametrically opposite positionswith respect to this hole and inclined outwards.

Each of the projections 85 has a generally radial hole 86 (FIG. 3)communicating with the annular chamber 79 through a duct 87. The cap 72has a frusto-conical surface 88 round the conical section 77 of the body67. This surface is spaced away from the surface of the section 77 andin conjunction with that section, with the annular projection 75 andwith the end wall of the cap 72, bounds an annular chamber 89communicating with the atmosphere through a plurality of holes 90. Theannular chamber 89 communicates with the annular chamber 71 through anaxial duct 91.

A duct 92 of conical shape formed inside the body 67 is coaxial with andpasses through t'his body. The duct. 92 ends in an outlet hole 93 ofsmall cross-sectionalarea and communicates at the other end with theinterior of the tubular body 64.

The'outside surface of the tubular body 64 located inside thecylindrical cavity 63, together with the surface of this cavity and themembrane 50, bound an an- 'nular chamber 94. This chamber is adapted tobe placed in communication with the interior of the tubular body 64 byaxial deformation of the membrane 50.

The annular chamber 94 also communicates with the exterior through aradial duct 95 (FIGS) and a duct 96 perpendicular to the axis of thecylindrical body 41 and formed inside this body. The duct 96 isconnected through a connector 97 with a tube 98 adapted to supply theabrasive composition to the interior of the annular chamber 94.

OPERATION OF THE DEVICE 4 The device 9 described above operates in thefollowingway. When the device is not in operation, neither the atomizingair nor the control air are supplied to the device. whereas on the otherhand theabrasive composition fills the annular chamber 94. This chamberis closed by the membrane 50 which is forced by the rod 24 to close theend of the tubular body 64. The rod 24 is pressed against the membrane50 by the spring 35.

Before spraying commences, the ring 33 is unscrewed and by means of thehead 32 the pin 31 is rotated so as to be located in the required axialposition inside the cavity 20. The axial position of the pin 31 dependson the quantity of abrasive composition which it is required to sprayand on the pressure at which this composition is supplied. When therequired axial position is reached, the pin 31, is locked byretightening the ring 33. This defines the possible movement of the "rod24, .of the cup-shaped body 26, and therefore of the membrane 50, and soadjusts the size of the passage which establishes communication betweenthe annular chamber 94 and the abrasive composition outlet duct 92. Thispassage is formed between the membrane 50 and the free end of thetubular body 64 when the membrane 50 is axially deformed under thepressure of the abrasive composition and comes into contact with thefree end of the rod 24. t

This adjustment makes it possible to compensate for any load losses inthe ducts through which the abrasive composition is supplied to thevarious devices 9 mounted on the same hood 4, so as to equalize thedelivery of all the device 9.

When the spraying begins, the tubes 39 and 84 (FIG. 2) supply the device9 with control air and atomizing air at the same time. The atomizing airpasses through the tube 84 and the connector 83 to the interior of theduct 82, from which it passes through the duct 81 (FIG. 3) into theannular chamber 71. Same of the atomizing air passes from these alongthe passage 91 to reach the interior of the annular chamber 89. Fromthere it passes out through the holes 90 and mixes with the abrasivecomposition emerging through the hole 93.

The other atomizing air inside the chamber 71 passes through the duct 80into the annular chambers and 79 and from the second of these it passesthrough the ducts 87 to the outlet holes 86 formed in the projections85.

The control air, on the other hand, passes through the Connector 38(FIG. 2) into the annular chamber 36 (FIG. 3) and exerts a pressure onthe cup-shaped body 26, forcing this body to slide inside the cavity 20against the action of the spring 35 until the free end of the pin 31 isin contact with the internal surface of the end wall 25 of the body 26.

The sliding movement of the body 26 and therefore of the rod 24 axiallyfrees the membrane 50 so that, under the thrust due to the abrasivecomposition under pressure inside the chamber 94, the membrane isdeformed so as to move away from the end of the tubular body 64. Thedeformation of the membrane 50 thus permits the abrasive composition topass into the duct 92 and escape through the outlet holes 93.

The volume of abrasive composition contained inside the duct 92 andinside the tubular body 64 is very small, so that the disadvantage ofdripping of the abrasive material when the device is not in operation ispractically eliminated.

The tubular body 64, beinga separate member mounted in the cylindricalbody 41, can easily be replaced when worn out by the abrasive materialpassing through it.

What I claim is:

l. A spraying device for an abrasive liquid composition, comprising anelongated body having a longitudinal axis, a nozzle for ejectingabrasive composition and atomizing air, the nozzle being connectedlongitudinally to one end of the body, a passage leading from theexterior into the body and communicating with the nozzle, the abrasivecomposition being adapted to be admitted through such passage andexpelled through the nozzle, a membrane located in such passage, and

regulating means for varying the position of the membrane in order tovary the flow of abrasive composition through the passage; saidregulating means including a longitudinally arranged single-actingpneumatic cylinder having a-plunger adapted to co-operate with themembrane, and a pin member arranged longitudinally and being adjustablefrom outside the body to limit the permissible movement of the plunger,said passage including a chamber in which is secured a tubular memberhaving a free end exposed in said chamber, said abrasive compositionbeing adapted to flow over said free end before reaching the nozzle, themembrane being supported around its full periphery in the body with afirst of its surfaces defining a wall of said chamber facing the freeend of the tubular member, the plunger of the pneumatic cylinder beingadapted to bear on a portion of the second surface of the membraneopposite the free end of the tubular member to regulate the distance ofthe membrane from the free end of the tubular member and thus regulatethe flow of abrasive composition.

2. The spraying device of claim 1, in which the body has a ductconnecting the chamber outside the tubular member to the exterior, thisduct being adapted to be connected to a source of abrasive composition.

3. The spraying device of claim 1, in which the tubular member isreplaceably mounted in the body.

4. The spraying device of claim 1, including resilient means biasing theplunger of the pneumatic cylinder towards a position in which theplunger presses the membrane against the free end of the tubular memberto preven flow of abrasive composition and including means a apted to amu compressed air to sue cylinder to overcome the resilient means.

1. A spraying device for an abrasive liquid composition, comprising anelongated body having a longitudinal axis, a nozzle for ejectingabrasive composition and atomizing air, the nozzle being connectedlongitudinally to one end of the body, a passage leading from theexterior into the body and communicating with the nozzle, the abrasivecomposition being adapted to be admitted through such passage andexpelled through the nozzle, a membrane located in such passage, andregulating means for varying the position of the membrane in order tovary the flow of abrasive composition through the passage; saidregulating means including a longitudinally arranged single-actingpneumatic cylinder having a plunger adapted to co-operate with themembrane, and a pin member arranged longitudinally and being adjustablefrom outside the body to limit the permissible movement of the plunger,said passage including a chamber in which is secured a tubular memberhaving a free end exposed in said chamber, said abrasive compositionbeing adapted to flow over said free end before reaching the nozzle, themembrane being supported around its full periphery in the body with afirst of its surfaces defining a wall of said chamber facing the freeend of the tubular member, the plunger of the pneumatic cylinder beingadapted to bear on a portion of the second surface of the membraneopposite the free end of the tubular member to regulate thE distance ofthe membrane from the free end of the tubular member and thus regulatethe flow of abrasive composition.
 2. The spraying device of claim 1, inwhich the body has a duct connecting the chamber outside the tubularmember to the exterior, this duct being adapted to be connected to asource of abrasive composition.
 3. The spraying device of claim 1, inwhich the tubular member is replaceably mounted in the body.
 4. Thespraying device of claim 1, including resilient means biasing theplunger of the pneumatic cylinder towards a position in which theplunger presses the membrane against the free end of the tubular memberto prevent flow of abrasive composition, and including means adapted toadmit compressed air to such cylinder to overcome the resilient means.